Systems analysis of the hemodynamics in tetralogy of Fallot: based on Fortran IV computer simulation.

A hemodynamic model has been developed for the patient with tetralogy of Fallot based on electrical circuit analog and oxygen balance equations. A computer program has been written for the model in the Fortran IV computer language. With the computer model it has been possible to simulate the physiologic conditions during exercise, squatting and hypoxic episodes in tetralogy of Fallot. In addition, it has been possible to simulate the palliative effect of systemic-to-pulmonary shunt operations. Partial factorial analysis has been employed in the computer program to enable investigation of the physiologic interactions in tetralogy of Fallot. Graphical representations of the computer output are presented which demonstrate precise cause and effect relationships in exercise, squatting and hypoxic episodes. An explanation is advanced for the lack of correlation between resting arterial oxygen saturation and the incidence of hypoxic episodes.